Telephone service to the home has been provided by buried service wire. Typically each of these has included a pair of metallic conductors such as copper wires enclosed in a jacket.
The use of optical fibers in communications has grown significantly over the past few years. It is anticipated that their use will reach into the residential loop distribution system in the near future. For now, loop distribution cables which include insulated metallic conductors continue to be installed.
As one alternative, operating telephone companies have expressed a desire to install composite cables which include optical fibers as well as metallic conductors. Such a course of action of early placement of optical fibers in buried installations to customers' premises will facilitate the later transition from a metallic to an optical fiber operating system. Obviously, the first cost of installing optical fiber to customers' premises is minimized by such an approach. With such a composite cable, optical fiber can be provided to customers' premises awaiting the arrival of the optical fiber network and development of associated hardware and electronics.
Such composite cables will be placed by the same methods and apparatus as are used for installing buried copper cables. Accordingly, the optical fiber portion thereof is robust enough to withstand plowing and trenching and is capable of survival outside the host structure in a separate run to an optical fiber storage or termination point.
With such a cable structure in place, service will evolve from the metallic pairs to the optical fibers. Simple telephone service can begin immediately over a metallic pair of conductors. Other metallic conductor pairs of the distribution and service cable can serve as secondary lines or alarm circuits. Initially, the optical fiber unit may be used to provide cable television or retained for later use.
At a later date, more sophisticated offerings which require increased bandwidth and customer interaction such as, for example, electronic newspapers and mail, catalogs and shopping, banking and business activities and data and computer functions may be served through a remote terminal. For this application, metallic conductor pairs may provide power to on-premise electronics or serve as control circuits. Still later, all offerings may be provided over the optical fiber media, but power still will have to be provided for on-site electronics by the power or telephone operating company. Providing power from a central office source through these structures should result in reliable telecommunications during power outages. Also, the copper conductor pairs may have other uses such as circuit maintenance, for example.
An important consideration relates to the repair of buried optical fiber cable. Should the optical fiber cable which extends to the home or to a splice point be damaged by construction equipment or by a homeowner, provisions must be made for repairing the cable without entering the splice on the distribution cable. There may be sufficient slack in the severed cable which extends to the home to permit splicing. If not, the cable from a buried splice closure to the home may be replaced, or an additional length of cable may be installed in the vicinity of the damaged portion, requiring two closures.
Whatever splice arrangement is used, such as the so-called rotary mechanical splice, for example, provisions must be made for protecting the splice and storing necessary fiber slack. The rotary mechanical splice is disclosed in U.S. Pat. No. 4,545,644 which issued on Oct. 8, 1985 in the names of G. F. DeVeau and C. Miller. Protection of the splice is accomplished by providing a closure which is destined to be buried and which is capable of maintaining its integrity in a buried environment.
Desirably, such a closure must possess certain attributes. For example, it must be low in cost, it must be adept to splice low fiber count cables and designed so that an encapsulant which is introduced thereto will reach the splice and the stored fiber. Furthermore, inasmuch as fiber ready cables, such as that, for example, disclosed in application Ser. No. 19,719 filed on Feb. 27, 1987, pending, in the names of F. J. Mullin and W. C. Reed includes copper as well as optical fibers, the sought-after closure must be able to accommodate the splicing of copper conductors as well as optical fibers. Also, the sought after closure should be capable of resisting the crushing effect of the earth above it as well as the pulling forces which may be applied to the cables.
In another approach, instead of incorporating optical fiber along with metallic conductors in a single cable structure and await later connection of the optical fiber while using presently the metallic conductors optical fiber cable may be extended from a remote terminal to a buried closure. The buried closure becomes a splice point when the fiber is to be connected to a home at some later date. For this arrangement to be economically feasible, the cost of the buried closure must be relatively low.
Seemingly, the prior art does not include such a closure which is inexpensively priced to be useful for use in providing a repair splice. Although the sought after closure may satisfy a need in the immediate future for repair splices, it may become useful to provide splice points now for future buried optical fiber which will be extended to customer premises.